ADP1853ACPZ-R7 datasheet(15/28 Pages) AD

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Data Sheet

ADP1853

Rev. 0 | Page 15 of 28

SHORT-CIRCUIT AND CURRENT-LIMIT

PROTECTION

When the output is shorted or the output current exceeds the

current limit set by the current-limit setting resistor (between

ILIM and CS) for eight consecutive cycles, the ADP1853 shuts

off both the high-side and low-side drivers and restarts the soft

start sequence every 10 ms, which is known as hiccup mode.

The SS node discharges to zero through an internal 3 kΩ

resistor during an overcurrent or short-circuit event. Figure 22

shows that the ADP1853 on a high current application circuit

maintains current-limit hiccup mode when the output is

shorted.

Figure 22. Current-Limit Hiccup Mode, 20 A Current Limit

ENABLE/DISABLE CONTROL

The EN pin is used to enable or disable the controller ADP1853;

the precision enable typical threshold is 0.63 V. When the

voltage at EN rises above the threshold voltage, the controller is

enabled and starts normal operation after initialization of the

internal oscillator, references, settings, and the soft start period.

When the voltage at EN drops to typically 30 mV (hysteresis)

below the threshold voltage, the driver and the internal

controller circuits in the ADP1853 are turned off. The initial

settings are still valid; therefore re-enabling the controller does

not change the settings until the power at the VIN pin is cycled.

In addition, the EN signal does not shut down the LDO at

VCCO, which is always active when VIN is above the UVLO

threshold.

For the purpose of start-up power sequencing, the startup of the

ADP1853 can be programmed by connecting an appropriate

resistor divider from the master power supply to the EN pin, as

shown in Figure 23. For instance, if the desired start-up voltage

from the master power supply is 10 V, R1 and R2 can be set to

156 kΩ and 10 kΩ, respectively.

Figure 23. Optional Power-Up Sequencing Circuit

CH1 10V

M2ms

A CH1

11.2V

CH3 500mV

CH4 10A

Ω

INDUCTOR

CURRENT

ADP1853

RTOP

RBOT

VOUT

MASTER

SUPPLY

VOLTAGE

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